Nowadays lighting systems or stage lights on the market are with the function of adjusting the size or the shape of their illuminated areas. Take stage lights for example, the size and the shape of the illuminated area are adjusted according to performer's show on the stage in order to attain perfect light effects.
The prior art for adjusting the size and the shape of the illuminated area of a lighting system are classified as following:
(1) Two optical elements are rotated around or moved about the incident optical axis so that the size of the illuminated area is adjusted. U.S. Pat. No. 4,101,957 discloses an illuminating lamp which provides for varying both the intensity of light output and the size of the illuminated area. The intensity of light output and the size of the illuminated area are varied by moving the position of a lens which is on the incident optical axis. Moreover, U.S. Pat. No. 5,584,568 discloses a lighting apparatus which has a lighting filament, a first lens disposed at a fixed distance from the filament and a sleeve carrying a second lens for sliding relative to the box. The size of the illuminated area varies with the position of the second lens. However, the prior art mentioned above may only adjust the size of the illuminated area. The shape of the illuminated area can not be adjusted.
(2) The relative positions of optical elements which are along the incident optical axis are adjusted so that the size and the intensity distribution of the illuminated area are adjusted. U.S. Pat. No. 6,986,593 discloses a lighting system which provides for varying the size of the illuminated area. The radiated angle of the light source, i.e. light emitter diode module, is varied by adjusting the position of an object lens so that the size of the illuminated area is varied. In addition, U.S. Pat. No. 6,866,401 discloses a lamp which provides for varying the size of the illuminated area. The light source of the lamp also adopts light emitter diode module. The illuminated area of the lamp is varied when the light source driven by a zoom apparatus is moved forward or backward. The zoom apparatus is slidably adjustable or rotatably adjustable. However, the prior art mentioned above may only adjust the size of the illuminated area. The shape of the illuminated area can not be adjusted.
(3) Optical elements of a lighting system are interchanged so that the light path is changed and the shape of the illuminated area is therefore changed. U.S. Pat. No. 4,608,622 discloses a multi-functional optical source which changes the light path by a complicated mechanical assembly, i.e. a turn table. The turntable is rotatable to different predetermined positions relative to a collimated light source to produce selectable illuminated shape. U.S. Pat. No. 4,400,765 discloses an operating room light fixture with adjustable light pattern. The light path passes different reflect bodies and the illuminated shape is thus varied because the light path is changed. However, the prior art mentioned above adopts too many mechanical assemblies so that the lighting system is complicated and costs a lot of money. Moreover, the interchange of the illuminated shape is not continuous and not smooth because the physical limitation of the mechanical assemblies. Users feel less comfortable when adjusting the illuminated shape.
(4) Light emitter diode modules are controlled to produce different illuminated shape. U.S. Pat. No. 3,648,706, U.S. Pat. No. 4,392,187, and U.S. Pat. No. 6,796,690 all disclose a lighting system wherein its light source adopts a great number of light emitter diode groups and its control system are composed of control circuits and complex mechanisms. The control system controls the great number of light emitter diode groups to adjust the illuminated shape, the size of the illuminated area, the illuminated intensity and the illuminated direction. However, the prior art mentioned above adopts too many illuminants and the control system (control circuits and mechanisms) are too complicated.
(5) A projection light is interrupted by a rotatable disc which carries different patterns to adjust the size and the shape of an illuminated area of a lighting system. U.S. Pat. No. 5,665,305 discloses a lighting system equipped with a number of rotatable discs wherein each disc may carry a plurality of lens elements. The light passes through the discs and then projects on the illuminated area. Therefore when the light passes through different discs, the shape or the size of the illuminated area are changed according to the lens elements of the disc chosen by the user. U.S. Pat. No. 6,048,080 discloses a lighting system equipped with a rotatable disc wherein the disc carries a number of different lens elements. The light passes through the discs and projects on the illuminated area. Users may rotate the disc to choose a desired lens element. When the light passes through the chosen lens element, the shape or the size of the illuminated area are thus changed. Although the prior art mentioned above may adjust the illuminated shape, the interchange of the illuminated shape is not continuous and not smooth because the physical limitation of the mechanical assemblies. Users feel less comfortable when adjusting the illuminated shape.
In view of the above prior arts, although the size or the shape of the illuminated area is adjusted, the mechanical design or the control circuits of the lighting system are very complex. Moreover, the light sources in some prior arts adopt a great number of light emitter diodes and thus lighting systems require higher cost. The prior arts don't conform to the design trend of the lighting systems under present enterprises' requirements, cost down for example. Therefore, a solution of continuously and smoothly adjusting the size or the shape of the illuminated area is the subject matter of the present invention.